Optical disc apparatus and optical disc provided with quality estimetor for generating quality value of recording quality of optical disc

ABSTRACT

In an optical disc apparatus that records and reproduces data onto and from an optical disc in units of predetermined block, an information divider divides the data so as to reduce an amount of the data included in each of blocks when a recording state of the optical disc does not satisfy a predetermined criterion, and reproduces recording data in units of the block by adding sub-information including a value indicating the amount of the data included in each of the blocks. An error-correction encoder circuit encodes the recording data in a first error-correction code format, and a recorder converts encoded recording data into a recording signal, and records the recording signal onto the optical disc. A quality evaluator circuit produces an evaluation value indicating a recording quality based on a result of reproducing the recording signal recorded on the optical disc.

CROSS-REFERENCE TO RELATED APPLICATION

This is an application, which claims priority to Japanese patentapplication No. JP 2016-046422 as filed on Mar. 10, 2016, the contentsof which are incorporated herein by reference.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

This disclosure relates to an optical disc apparatus that records andreproduces data onto and from an optical disc, and relates to an opticaldisc onto which data is optically recorded.

2. Description of the Related Art

Many types of optical discs such as a DVD, a Blu-ray (a registeredtrademark) disc (hereinafter, referred to as a BD) are currently used asinformation recording media each for storing a video image, data, or thelike. From the viewpoint of space efficiency for storing the data, atechnique to improve the track density and a technique to improve theline density are present as techniques each to improve the recordingcapacity per volume without increasing the cost of the optical disc. Ithas been known for an optical disc that error-correction is executed inunits of a predetermined block (See Patent Document 1, for example).

Improvement of the storage density can be facilitated to improve therecording capacity of an optical disc. However, the number of bit errorsoccurring during reproduction is also increased associated with theimprovement of the density, and therefore, an error correcting codetechnique having improved error-correction capability has been proposed.

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: WO 2004/012190 A1

SUMMARY OF THE DISCLOSURE

The present disclosure provides an optical disc apparatus capable ofstably reproducing data recorded on an optical disc having an increaseddensity.

According to one aspect of the present disclosure, there is provided anoptical disc apparatus that records and reproduces data onto and from anoptical disc in units of predetermined block. The optical disc apparatusincludes an information divider, an error-correction encoder circuit, arecorder, and a quality evaluator circuit. The information dividerdivides the data so as to reduce an amount of the data included in eachof blocks when a recording state of the optical disc does not satisfy apredetermined criterion, and reproduces recording data in units of theblock by adding sub-information including a value indicating the amountof the data included in each of the blocks. The error-correction encodercircuit encodes the recording data in a first error-correction codeformat. The recorder converts encoded recording data into a recordingsignal, and records the recording signal onto the optical disc. Thequality evaluator circuit produces an evaluation value indicating arecording quality based on a result of reproducing the recording signalrecorded on the optical disc.

The present disclosure provided the optical disc apparatus capable ofstably reproducing data recorded on an optical disc having an increaseddensity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a configuration of an optical discapparatus 10 according to an embodiment.

FIG. 2 is a format diagram of a configuration of a space format of anoptical disc 100 used in the optical disc apparatus 10 of FIG. 1.

FIG. 3 is a format diagram of a configuration of a standard format usedin encoding executed in units of a data block by an error-correctionencoder circuit 106 of FIG. 1.

FIG. 4 is a format diagram of a configuration of a recording format thatcorresponds to the standard format of FIG. 3.

FIG. 5 is a format diagram of a configuration of a shortened format usedin encoding executed in units of the data block by the error-correctionencoder circuit 106 of FIG. 1.

FIG. 6 is a format diagram of a configuration of a recording format thatcorresponds to the shortened format of FIG. 5.

FIG. 7 is a format diagram of contents of recording data of the standardformat of FIG. 3.

DETAILED DESCRIPTION OF THE EMBODIMENTS

One non-limiting and exemplary embodiment will be described below indetail with reference to the drawings as appropriate. It is noted thatno detailed description beyond necessity may be made. For example, nodetailed description of items already known well and no redundantdescription for substantially same configurations may be made. This isto avoid any unnecessary redundancy in the following description and tofacilitate understanding of those skilled in the art.

The accompanying drawings and the following description are provided forthose skilled in the art to fully understand the present disclosure, andthen, any limitation is not intended for the subject matter described inclaims.

Non-Limiting and Exemplary Embodiment 1. Configuration

FIG. 1 is a block diagram of a configuration of an optical discapparatus 10 according to the present embodiment. Referring to FIG. 1,the optical disc apparatus 10 includes an optical head 101, a spindlemotor 102, a servo controller 103, a laser driving circuit 104, a datamodulator circuit 105, an error-correction encoder circuit 106, areproduced signal decoder circuit 107, a data demodulator circuit 108,an error-correction decoder circuit 109, a signal quality evaluatorcircuit 110, an address reproducer circuit 111, a format selectorcircuit 112, a system controller 115, an interface circuit (hereinafter,referred to as an I/F circuit) 114, and a read only memory (ROM) 116.

The optical disc apparatus 10 records and reproduces user data onto andfrom an optical disc 100. On the optical disc 100, a track is disposedin a spiral shape from an inner circumference thereof to the outercircumference thereof. The track includes a groove track formed by agroove and a land track formed between the adjacent groove tracks. Theuser data is recorded on both of the groove track and the land track.

The spindle motor 102 rotates the optical disc 100. The optical head 101irradiates a light beam to the optical disc 100, to record user dataonto the optical disc 100 and reproduce the user data from the opticaldisc 100.

The servo controller 103 controls the optical head 101 and the spindlemotor 102 to condense the light beam irradiated from the optical head101 to the optical disc 100 on the track disposed on the optical disc100, to scan the condensed light beam thereon. Then, the servocontroller 103 controls the optical head to move so as to access atarget track. The servo controller 103 controls the position of theoptical head 101 and the rotation number of the spindle motor 102 forthe optical head 101 to scan the optical disc 100 at a predeterminedline velocity.

The I/F circuit 114 receives user data to be recorded on the opticaldisc 100, from a host apparatus 113. The I/F circuit 114 sends user datareproduced from the optical disc 100, to the host apparatus 113.

The error-correction encoder circuit 106 adds a parity forerror-correction, to the user data received from the I/F circuit 114 toform encoded data.

The data modulator circuit 105 produces a modulated signal by modulatinga predetermined pulse signal using a predetermined modulation ruleaccording to the encoded data including the parity sent from theerror-correction encoder circuit 106. The encoded data of this modulatedsignal is recorded in the track on the optical disc 100.

The laser driving circuit 104 converts the modulated signal into anoptical pulse to accurately form a mark on the optical disc 100, anddrives a laser of the optical head 101 according to the convertedoptical pulse. The mark is formed on the optical disc 100 by the heat ofthe irradiated laser.

On the other hand, the user data recorded on the optical disc 100 isreproduced by the reproduced signal decoder circuit 107, the datademodulator circuit 108, and the error-correction decoder circuit 109.

The optical head 101 irradiates the light beam to the optical disc 100,and then, detects a reflected light beam from the optical disc 100. Theoptical head 101 reproduces a reproduced signal based on the detectedreflected light beam, and outputs the reproduced signal.

The reproduced signal decoder circuit 107 decodes the reproduced signaloutputted by the optical head 101 to produce a decoded signal. Forexample, this is realized by a PRML signal processing techniqueaccording to which an expected value waveform closest to the reproducedsignal is selected from the comparison between the reproduced signal andexpected value waveforms, and a binary signal to be the source of theexpected value waveform is outputted as the decoded signal. Thereproduction performance when handling a higher line density can beacquired by employing the condition under which the width of aninter-symbol interference is set to be longer than a predeterminedwidth.

The data demodulator circuit 108 demodulates the encoded data from thedecoded signal using a predetermined modulation rule.

The error-correction decoder circuit 109 corrects errors in thedemodulated encoded data to recover the user data.

The signal quality evaluator circuit 110 measures the quality such asdistortion and amplitude dispersion of the reproduced signal and thelike based on the result of the decoding of the decoded signal by thereproduced signal decoder circuit 107. A maximum likelihood sequentialerror (MLSE) index is used as a signal quality evaluation technique thathandles the PRML signal processing technique. The MLSE indexquantitatively evaluates the magnitude of the error between thereproduced signal and the expected value waveform. The recordingcondition of the mark recorded on the track of the optical disc 100 canbe evaluated by the MLSE index.

The address reproducer circuit 111 reproduces address information from awarble signal corresponding to the meandering of the track of theoptical disk 100 detected by the optical head 101, and then, outputs thereproduced address information. The track of the optical disc 100 isformed with meandering at predetermined periods, and the addressinformation is included therein for the position of the track to beknown by modulating the predetermined period.

The format selector circuit 112 selects the error-correction format ofthe encoded data to be recorded on the track of the optical disc 100.The error-correction encoder circuit 106 and the error-correctiondecoder circuit 109 operate according to the selected error-correctionformat.

The ROM 116 includes a flash memory. The ROM 116 has a program storedtherein in advance, which is executed by the system controller 115 tocontrol the overall optical disc apparatus 10.

The system controller 115 controls each of the circuits and controls thecommunication with the host apparatus 113, by reading out and executingthe program stored in the ROM 116. In FIG. 1, for convenience, no arrowis shown to indicate the control for the constituent elements other thanthe system controller 115 to the format selector circuit 112. The systemcontroller 115 of the optical disc apparatus 10 according to the presentembodiment determines a space on the optical disc 100 from the addressinformation outputted by the address reproducer circuit 111, andcontrols the format selector circuit 112 to record the encoded data inan error-correction format corresponding to the space. The systemcontroller 115 also determines the state of degradation of the opticaldisc 100 based on the state of the recording of the mark evaluated bythe signal quality evaluator circuit 110, and determines the amount ofrecording data to be included in units of the block of theerror-correction format.

FIG. 2 is a format diagram of a configuration of a space format of theoptical disc 100 used in the optical disc apparatus 10 of FIG. 1.Referring to FIG. 2, on the inner circumference side of the optical disc100, an inner zone is disposed that has management information and thelike recorded therein to manage the use status and the like of the trackof the optical disc 100. In the rest of the space of the optical disc100, a data zone is disposed to record therein the user data transmittedfrom the host apparatus 113. In the data zone of the optical disc 100, astandard format is used as the encoding format and, in the inner zonethereof, a shortened format is used. The system controller 115 controlsthe format selector circuit 112 to switch the encoding formatcorresponding to whether the space for the recording is the data zone orthe inner zone.

FIG. 3 is a format diagram of a configuration of the standard formatused in encoding in units of the data block by the error-correctionencoder circuit 106 of FIG. 1. A Reed-Solomon iterated code using 10bits as one symbol is used as the error-correction code. An inner codeadds an inner code parity code of four symbols to 232 symbols of therecording data. The number of inner codes per one data block is906+76=982. An outer code adds an outer code parity code of 76 symbolsto 906 symbols of the recording data. The number of outer codes per onedata block is 232+4=236. One data block includes the recording data of906×232=210,192 symbols, that is, 210,192 (symbols)×10 (bits)/8(bits)=262,740 bytes. In the error-correction encoder circuit 106, theuser data transmitted from the host apparatus 113 is added with an errordetection parity code of four bytes for each 2,048 bytes to include2,052 bytes. 128 sets of these 2,052 bites become 262,656 bytes. Therecording data of 262,740 bytes in total is formed by further addingthereto 84 bytes of the control data such as the address informationindicating the position to be recorded at, and the like, added with anerror-correction parity code for the control data (an error-correctionparity code for executing error-correction for the control data). Therecording data of these 262,740 bytes is encoded according to the formatof the Reed-Solomon iterated code to be the encoded data. The controldata is an example of sub-information, and the sub-information includesthe control data and the error-correction parity code for the controldata.

FIG. 4 is a format diagram of a configuration of a recording format of amodulated signal in units of the data block by the data modulatorcircuit 105 for the standard format of FIG. 3. Referring to FIG. 4, theencoded data that is error-correction-encoded is modulated using onecode of the inner codes of the Reed-Solomon iterated code format shownin FIG. 3 as one frame and using a run-length limited (RLL) (1, 10)modulation rule. A synchronization pattern using 12T not included in themodulation rule is added at the head of the frame. In this case, Tdenotes a reference period of the modulation. In order to avoidinclusion of any lower component in the frequency property of themodulated signal, a DC control bit equalizing the ratios of the mark andthe space is inserted at predetermined intervals, and the length of theone frame is 3,642T. The number of frames is equal to the number ofinner codes and is 982 frames. A run-in having a length of 5,463T isadded at the head of the data block, and a run-out having a length of1,821T is added at the end terminal. The “Run-in” is a space used forcontrol of the amplitude of the reproduced signal and the like, suchthat the reproduced signal decoder circuit 107 can execute stable signalprocessing from the head of the frame 0. The “Run-out” is a buffer spaceto avoid any overlapping of the data blocks and generation of any voidtherebetween when the succeeding data block is recorded.

FIG. 5 is a format diagram of a configuration of a shortened format usedin encoding in units of the data block by the error-correction encodercircuit 106 of FIG. 1. Referring to FIG. 5, in a manner similar to thatof the standard format, the Reed-Solomon iterated code which uses 10bits as one symbol is used as the error-correction code. As to the innercode, the inner code parity code of four symbols is added to therecording data of 232 symbols. The number of inner codes per one datablock is 45+76=121. As to the outer code, the outer code parity code of76 symbols is added to the recorded data of 45 symbols. The number ofouter code per one data block is 232+4=236. The outer code in thestandard format includes 76 symbols of the outer code parity code for906 symbols of the recording data. On the other hand, the outer code inthe shortened format includes 76 symbols of the inner code parity codefor 45 symbols of the recording data. Namely, in the shortened format,the inner code is same as that of the standard format. On the otherhand, the redundancy degree of the outer code is higher than that of thestandard format. Therefore, the recording data is small, but theerror-correction capability of the outer code is very high.

One data block includes 232×45=10,440 symbols, that is, the recordingdata of 13,050 bytes. In the inner zone, the system controller 115 sendsthe management information and the like to manage the status of the useof the track of the optical disc 100 to the error-correction encodercircuit 106 through the I/F circuit 114. In the error-correction encodercircuit 106, an error detection parity code of four bytes is added toeach 2,048 bytes to be 2,052 bytes. Six sets of these 2,052 bytes become12,312 bytes. The recording data of 13,050 bytes in total is formed byfurther adding thereto 738 bytes formed by adding the control data suchas the address information indicating the position to be recorded at,and the like, and the error-correction parity code for the control data.The recording data of these 13,050 bytes is encoded according to theshortened format of the Reed-Solomon iterated code, to be the encodeddata.

FIG. 6 is a format diagram of a configuration of a recording format ofthe modulated signal in units of the data block by the data modulatorcircuit 105 for the shortened format of FIG. 5. Referring to FIG. 6, themodulated signal is produced by modulating the pulse signal according tothe encoded data that is error-correction-encoded, using one code of theinner codes of the shortened format of the Reed-Solomon iterated codeshown in FIG. 5 as one frame, and using the RLL (1, 10) modulation rule.The synchronization pattern using 12T not included in the modulationrule is added to the head of the frame. In order to avoid inclusion ofany lower component in the frequency property of the modulated signal, aDC control bit equalizing the ratios of the mark and the space isinserted at predetermined intervals and the length of the one frame is3,642T. The configuration of the one frame is same as that of thestandard format. The number of frames is equal to the number of innercodes of the shortened format and is 121 frames. A run-in having alength of 5,463T is added to the head of the data block, and a run-outhaving a length of 1,821T is added to the end terminal of the datablock.

In the standard format and the shortened format, the run-in and therun-out are common thereto, and then, the length thereof is 7,284T intotal and corresponds to the length of two frames. Therefore, the lengthof the data block of the standard format is 3,642T×984 frames, and thelength of the data block of the shortened format is 3,642T×123 frames.The length of the data block of the shortened format is ⅛ of the lengthof the data block of the standard format. As shown in FIG. 2, theaddress information is added by 0x80 in units of one data block of thestandard format, and the address information is added by 0x10 in unitsof one data block of the shortened format. The length of the data blockof each of the recording and the reproduction is switched over betweenthe shortened format of the inner zone and the standard format of thedata zone. In this case, the relation is maintained to be constantbetween the physical position on the track of the optical disc 100 andthe address information. When the position is located on the borderbetween the inner zone and the data zone, the system controller 115 canaccess any data block at an arbitrary position on the optical disc 100using the address information acquired from the address reproducercircuit 111 without especially executing the switching of the processingconditions and the like.

2. Operation

The operations of the optical disc apparatus 10 of FIG. 1 will bedescribed.

The operation for recording data onto the track of the data zone of theoptical disc 100, which is executed by the optical disc apparatus 10 ofFIG. 1, will be described.

Referring to FIG. 1, the I/F circuit 114 acquires the user data and thelogic address of the recording destination transmitted from the hostapparatus 113. The user data is divided into data blocks of the unitsaccording to the standard format, to be sent to the error-correctionencoder circuit 106 by each data block.

The error-correction encoder circuit 106 adds a parity code to correcterrors during the reproduction, to the user data in units of the datablock, and then, produces the encoded data.

The data modulator circuit 105 produces a modulated signal by modulatingthe pulse signal using the predetermined modulation rule, according tothe encoded data having the parity code added thereto.

In order to accurately form a recording mark on the optical disc 100,the laser driving circuit 104 converts a pulse signal into a castle-typepulse waveform signal according to the modulated signal, and then,outputs a driving signal to drive the laser to the optical head 101.

The optical head 101 records the mark that corresponds to the modulatedsignal by irradiating a laser pulse to the position on the optical disc100, where the position corresponds to the logic address of therecording destination.

The system controller 215 controls the recording operation. The systemcontroller 115 determines the position to be recorded at on the opticaldisc 100 based on the logic address of the recording destinationacquired by the I/F circuit 114, and moves the optical head 101 to thetarget position by controlling the servo controller 103. Before arrivingat the track to be the target position, the system controller 115instructs the operation in the standard format through the formatselector circuit 112 to cause the error-correction encoder circuit 106to operate. The data modulator circuit 105 also outputs the modulatedsignal in the recording format shown in FIG. 4 corresponding to thestandard format according to the designation from the format selectorcircuit 112. At the time of arrival at the target position, the systemcontroller 115 causes the data modulator circuit 105 and the laserdriving circuit 104 to operate to record the data.

FIG. 7 is a format diagram of an example of the content of the encodeddata in the standard format of the FIG. 3. As described above, therecorded data includes the user data of up to 262,144 bytes. When theuser data transmitted from the host apparatus 113 through the I/Fcircuit 114 is smaller than 262,144 bytes, as shown in FIG. 7, thesystem controller 115 adds non-valid data whose value is zero for theinsufficient portion. The recording data is set to have 262,144 bytes asa total of the valid data and the non-valid data. The control dataincludes the value of the amount of the valid data in the recording datain addition to the address information. In the case where the amount ofthe valid data has been known, and it has been known that the value ofthe non-valid data is zero, when the data blocks are reproduced, then noinfluence is received from any error symbol generated in the non-validdata, and the error-correction capability for the valid data can beenhanced. This will be described below in detail.

The valid data is recorded before-aligned from the head of the datablock. When the amount of the valid data has been known, it can be knownat which position in the data block the valid data is recorded and atwhich position therein the non-valid data is recorded. Because it hasbeen known that the non-valid data is zero, even when any error isgenerated at the position of the non-valid data, any correction does notneed to be executed using the parity code. Therefore, the parity code issubstantially added only to the valid data. The error-correctioncapability can be enhanced because the parity code can be added tosmaller data by reducing the amount of the valid data.

Before executing the recording of the user data, the track alreadyrecorded on the optical disc 100 is reproduced, or test recording isexecuted and reproduction is executed. In this case, the signal qualityevaluator circuit 110 measures the MLSE index to evaluate the quality ofthe recording and the reproduction onto and from the optical disc 100.When the MLSE index indicates securing of an excellent qualitydetermined in advance, the user data of 262,144 bytes to be the maximumis assigned as the valid data to the recording data of one data block.When the MLSE index indicates degradation of the quality, to handle withthe errors increased by the degradation, the amount of the user data tobe assigned to the recording data of one data block is reduced to beused as the valid data, and the rest is set to be the non-valid data.Concretely speaking, the system controller 115 make the followingsetting such that the amount of the user data to be assigned to one datablock, that is, the amount of the valid data is reduced as the qualityindicated by the MLSE index is lower. Based on this, the value of thereduced amount of the valid data is recorded as the control data.

The operation of recording data onto the track in the inner zone of theoptical disc 100 of the optical disc apparatus 10 of FIG. 1 will bedescribed.

In the inner zone, there are recorded the management informationrecorded therein to manage the status of the use of the track in thedata zone, and the status of switching or the like recorded in anothertrack when a fault such as a scratch is present. The data amount of themanagement information is small, but the management information isindispensable information to records and reproduces the user data ontoand from the optical disc 100. It is especially important also for thehigh-density optical disc 100 to secure the relatively high reproductionperformance. Updating of the management information frequently occurs.Therefore, the length of the data block of the inner zone isadvantageously short such that a large number of recording sessionsassociated with the updating of the management information can besecured. From these conditions, the shortened format shown in FIG. 5 issuitable whose redundancy degree is increased by setting the data blockto be small for a small amount of recording data and by securing theparity of the error-correction code by the same amount as that of thestandard format of the data zone.

In the inner zone, the management information produced by the systemcontroller 115 is sent to the error-correction encoder circuit 106through the I/F circuit 114.

The error-correction encoder circuit 106 forms the coded data by addingthe parity code to correct any error generated during the reproduction,to the management information.

The data modulator circuit 105 produces the modulated signal bymodulating the pulse signal using the predetermined modulation ruleaccording to the encoded data having the parity code added thereto.

In order to accurately form the recording mark on the optical disc 100,the laser driving circuit 104 converts the modulated signal into thecastle-type pulse waveform signal, and outputs the driving signal todrive the laser to the optical head 101.

The optical head 101 records the mark that corresponds to the modulatedsignal by irradiating the laser pulse to the position on the opticaldisc 100 at which the management information is recorded.

The system controller 115 controls the above recording operation. Thesystem controller 115 determines the position, at which the managementinformation is recorded on the optical disc 100, and controls the servocontroller 103 to move the optical head 101 to the target position.Before arriving at the track to be the target position, the systemcontroller 115 instructs the operation in the shortened format throughthe format selector circuit 112 to cause the error-correction encodercircuit 106 to operate. The data modulator circuit 105 also outputs themodulated signal in the recording format shown in FIG. 6 thatcorresponds to the shortened format according to the designation fromthe format selector circuit 112. When the optical head 101 arrives atthe target position, the data modulator circuit 105 and the laserdriving circuit 104 are caused to operate to record the data.

The reproduction operation of the optical disc apparatus 10 of FIG. 1will be described.

The identification of the reproduction position for the optical disc 100is same as the identification operation of the recording position in therecording operation in either the data zone or the inner zone. At thetime for the position of the data block to be reproduced, the systemcontroller 115 causes the reproduced signal decoder circuit 107, thedata demodulator circuit 108, the error-correction decoder circuit 109,and the format selector circuit 112 to operate to reproduce the userdata or the management information. In the data zone, the operation isexecuted according to the standard format shown in FIGS. 3 and 4. In theinner zone, the operation is executed according to the shortened formatshown in FIGS. 5 and 6.

The reproduced signal decoder circuit 107 selects the expected valuewaveform that is the closest to the reproduced signal from thecomparison between the reproduced signal and the expected valuewaveforms, and outputs a binary signal to be the source of the expectedvalue waveform as the decoded signal.

The data demodulator circuit 108 demodulates the decoded signal intoencoded data using the predetermined modulation rule and theerror-correction decoder circuit 109 corrects errors in the demodulatedencoded data to recover the user data or the management information.

In the data zone, the error-correction decoder circuit 109 first readsout the information on the amount of the valid data included in thecontrol data. The error-correction decoder circuit 109 executes theerror-correction process for the control data using the error-correctionparity code for the control data, to acquire the information on theamount of the valid data. When the amount of the valid data is less than262,144 bytes, as described in the example of FIG. 7, the value of thesymbol corresponding to the non-valid data is set to be zero regardlessof the output result of the data demodulator circuit 108, andthereafter, the error-correction process for the inner code and theouter code is started. Thus any error of the symbol corresponding to thenon-valid data is corrected in advance, and the error-correction caneffectively be executed for the errors of the symbol of the valid data.

As described above, in order to enhance the error-correction capability,the non-valid data (that has been known and therefore noerror-correction is required therefor) needs to be known. Therefore, theamount of the valid data needs to be known in advance. In thesub-information including the amount of the valid data, the symbol errorrate during the reproduction is also equal to that of any other dataportion. In order to first accurately acquire the sub-information,desirably, the capability of the error-correction for thesub-information is further enhanced. Accordingly, the redundancy degreeof the second error-correction code format is set to be higher than theredundancy degree of the first error-correction code format.

3. Advantageous Effects or the Like

As described above, according to the present embodiment, according tothe optical disc 100 and the optical disc apparatus 10, stable recordingand stable reproduction of data can be done even when the optical disc100 having an increased track density and an increased line density isdegraded, by controlling the amount of the data to be in a range thatenables the error-correction. Very high reproduction performance can besecured for the management information indispensable for the recordingand reproduction of the optical disc 100 by using the shortened formathaving an increased redundancy degree.

This disclosure can be applied to an optical disc and an optical discapparatus that records and reproduces data.

What is claimed is:
 1. An optical disc apparatus that records and reproduces data onto and from an optical disc in units of predetermined block, the optical disc apparatus comprising: an information divider that divides the data so as to reduce an amount of the data included in each of blocks when a recording state of the optical disc does not satisfy a predetermined criterion, and reproduces recording data in units of the block by adding sub-information including a value indicating the amount of the data included in each of the blocks; an error-correction encoder circuit that encodes the recording data in a first error-correction code format; a recorder that converts encoded recording data into a recording signal, and records the recording signal onto the optical disc; and a quality evaluator circuit that produces an evaluation value indicating a recording quality based on a result of reproducing the recording signal recorded on the optical disc.
 2. The optical disc apparatus according to claim 1, wherein the sub-information includes control data that includes a value indicating the amount of the data included in each of the blocks; and an error-correction parity code for the control data used when error-correcting the control data with a second error-correction code format, and wherein a redundancy degree of the second error-correction code format is higher than a redundancy degree of the first error-correction code format. 